[PATCH RFC net-next 11/14] tracing: allow eBPF programs to be attached to events
From: Alexei Starovoitov
Date: Fri Jun 27 2014 - 20:08:34 EST
User interface:
cat bpf_123 > /sys/kernel/debug/tracing/__event__/filter
where 123 is an id of the eBPF program priorly loaded.
__event__ is static tracepoint event.
(kprobe events will be supported in the future patches)
eBPF programs can call in-kernel helper functions to:
- lookup/update/delete elements in maps
- memcmp
- trace_printk
- load_pointer
- dump_stack
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxxxx>
---
include/linux/ftrace_event.h | 5 +
include/trace/bpf_trace.h | 29 +++++
include/trace/ftrace.h | 10 ++
include/uapi/linux/bpf.h | 5 +
kernel/trace/Kconfig | 1 +
kernel/trace/Makefile | 1 +
kernel/trace/bpf_trace.c | 217 ++++++++++++++++++++++++++++++++++++
kernel/trace/trace.h | 3 +
kernel/trace/trace_events.c | 7 ++
kernel/trace/trace_events_filter.c | 72 +++++++++++-
10 files changed, 349 insertions(+), 1 deletion(-)
create mode 100644 include/trace/bpf_trace.h
create mode 100644 kernel/trace/bpf_trace.c
diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index cff3106ffe2c..de313bd9a434 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -237,6 +237,7 @@ enum {
TRACE_EVENT_FL_WAS_ENABLED_BIT,
TRACE_EVENT_FL_USE_CALL_FILTER_BIT,
TRACE_EVENT_FL_TRACEPOINT_BIT,
+ TRACE_EVENT_FL_BPF_BIT,
};
/*
@@ -259,6 +260,7 @@ enum {
TRACE_EVENT_FL_WAS_ENABLED = (1 << TRACE_EVENT_FL_WAS_ENABLED_BIT),
TRACE_EVENT_FL_USE_CALL_FILTER = (1 << TRACE_EVENT_FL_USE_CALL_FILTER_BIT),
TRACE_EVENT_FL_TRACEPOINT = (1 << TRACE_EVENT_FL_TRACEPOINT_BIT),
+ TRACE_EVENT_FL_BPF = (1 << TRACE_EVENT_FL_BPF_BIT),
};
struct ftrace_event_call {
@@ -536,6 +538,9 @@ event_trigger_unlock_commit_regs(struct ftrace_event_file *file,
event_triggers_post_call(file, tt);
}
+struct bpf_context;
+void trace_filter_call_bpf(struct event_filter *filter, struct bpf_context *ctx);
+
enum {
FILTER_OTHER = 0,
FILTER_STATIC_STRING,
diff --git a/include/trace/bpf_trace.h b/include/trace/bpf_trace.h
new file mode 100644
index 000000000000..2122437f1317
--- /dev/null
+++ b/include/trace/bpf_trace.h
@@ -0,0 +1,29 @@
+/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ */
+#ifndef _LINUX_KERNEL_BPF_TRACE_H
+#define _LINUX_KERNEL_BPF_TRACE_H
+
+/* For tracing filters save first six arguments of tracepoint events.
+ * On 64-bit architectures argN fields will match one to one to arguments passed
+ * to tracepoint events.
+ * On 32-bit architectures u64 arguments to events will be seen into two
+ * consecutive argN, argN+1 fields. Pointers, u32, u16, u8, bool types will
+ * match one to one
+ */
+struct bpf_context {
+ unsigned long arg1;
+ unsigned long arg2;
+ unsigned long arg3;
+ unsigned long arg4;
+ unsigned long arg5;
+ unsigned long arg6;
+};
+
+/* call from ftrace_raw_event_*() to copy tracepoint arguments into ctx */
+void populate_bpf_context(struct bpf_context *ctx, ...);
+
+#endif /* _LINUX_KERNEL_BPF_TRACE_H */
diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index 26b4f2e13275..ad4987ac68bb 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -17,6 +17,7 @@
*/
#include <linux/ftrace_event.h>
+#include <trace/bpf_trace.h>
/*
* DECLARE_EVENT_CLASS can be used to add a generic function
@@ -634,6 +635,15 @@ ftrace_raw_event_##call(void *__data, proto) \
if (ftrace_trigger_soft_disabled(ftrace_file)) \
return; \
\
+ if (unlikely(ftrace_file->flags & FTRACE_EVENT_FL_FILTERED) && \
+ unlikely(ftrace_file->event_call->flags & TRACE_EVENT_FL_BPF)) { \
+ struct bpf_context __ctx; \
+ \
+ populate_bpf_context(&__ctx, args, 0, 0, 0, 0, 0); \
+ trace_filter_call_bpf(ftrace_file->filter, &__ctx); \
+ return; \
+ } \
+ \
__data_size = ftrace_get_offsets_##call(&__data_offsets, args); \
\
entry = ftrace_event_buffer_reserve(&fbuffer, ftrace_file, \
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 03c65eedd3d5..d03b8b39e031 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -382,6 +382,7 @@ enum bpf_prog_attributes {
enum bpf_prog_type {
BPF_PROG_TYPE_UNSPEC,
BPF_PROG_TYPE_SOCKET_FILTER,
+ BPF_PROG_TYPE_TRACING_FILTER,
};
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
@@ -392,6 +393,10 @@ enum bpf_func_id {
BPF_FUNC_map_lookup_elem, /* void *map_lookup_elem(map_id, void *key) */
BPF_FUNC_map_update_elem, /* int map_update_elem(map_id, void *key, void *value) */
BPF_FUNC_map_delete_elem, /* int map_delete_elem(map_id, void *key) */
+ BPF_FUNC_load_pointer, /* void *bpf_load_pointer(void *unsafe_ptr) */
+ BPF_FUNC_memcmp, /* int bpf_memcmp(void *unsafe_ptr, void *safe_ptr, int size) */
+ BPF_FUNC_dump_stack, /* void bpf_dump_stack(void) */
+ BPF_FUNC_trace_printk, /* int bpf_trace_printk(const char *fmt, int fmt_size, ...) */
__BPF_FUNC_MAX_ID,
};
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index d4409356f40d..e36d42876634 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -80,6 +80,7 @@ config FTRACE_NMI_ENTER
config EVENT_TRACING
select CONTEXT_SWITCH_TRACER
+ depends on NET
bool
config CONTEXT_SWITCH_TRACER
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index 2611613f14f1..a0fcfd97101d 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -52,6 +52,7 @@ obj-$(CONFIG_EVENT_TRACING) += trace_event_perf.o
endif
obj-$(CONFIG_EVENT_TRACING) += trace_events_filter.o
obj-$(CONFIG_EVENT_TRACING) += trace_events_trigger.o
+obj-$(CONFIG_EVENT_TRACING) += bpf_trace.o
obj-$(CONFIG_KPROBE_EVENT) += trace_kprobe.o
obj-$(CONFIG_TRACEPOINTS) += power-traces.o
ifeq ($(CONFIG_PM_RUNTIME),y)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
new file mode 100644
index 000000000000..b7b394a0fd6e
--- /dev/null
+++ b/kernel/trace/bpf_trace.c
@@ -0,0 +1,217 @@
+/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ */
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/bpf.h>
+#include <linux/filter.h>
+#include <linux/uaccess.h>
+#include <trace/bpf_trace.h>
+#include "trace.h"
+
+/* call from ftrace_raw_event_*() to copy tracepoint arguments into ctx */
+void populate_bpf_context(struct bpf_context *ctx, ...)
+{
+ va_list args;
+
+ va_start(args, ctx);
+
+ ctx->arg1 = va_arg(args, unsigned long);
+ ctx->arg2 = va_arg(args, unsigned long);
+ ctx->arg3 = va_arg(args, unsigned long);
+ ctx->arg4 = va_arg(args, unsigned long);
+ ctx->arg5 = va_arg(args, unsigned long);
+ ctx->arg6 = va_arg(args, unsigned long);
+
+ va_end(args);
+}
+EXPORT_SYMBOL_GPL(populate_bpf_context);
+
+/* called from eBPF program with rcu lock held */
+static u64 bpf_load_pointer(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
+{
+ void *unsafe_ptr = (void *) r1;
+ void *ptr = NULL;
+
+ probe_kernel_read(&ptr, unsafe_ptr, sizeof(void *));
+ return (u64) (unsigned long) ptr;
+}
+
+static u64 bpf_memcmp(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
+{
+ void *unsafe_ptr = (void *) r1;
+ void *safe_ptr = (void *) r2;
+ u32 size = (u32) r3;
+ char buf[64];
+ int err;
+
+ if (size < 64) {
+ err = probe_kernel_read(buf, unsafe_ptr, size);
+ if (err)
+ return err;
+ return memcmp(buf, safe_ptr, size);
+ }
+ return -1;
+}
+
+static u64 bpf_dump_stack(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
+{
+ trace_dump_stack(0);
+ return 0;
+}
+
+/* limited trace_printk()
+ * only %d %u %x conversion specifiers allowed
+ */
+static u64 bpf_trace_printk(u64 r1, u64 fmt_size, u64 r3, u64 r4, u64 r5)
+{
+ char *fmt = (char *) r1;
+ int fmt_cnt = 0;
+ int i;
+
+ /* bpf_check() guarantees that fmt points to bpf program stack and
+ * fmt_size bytes of it were initialized by bpf program
+ */
+ if (fmt[fmt_size - 1] != 0)
+ return -EINVAL;
+
+ /* check format string for allowed specifiers */
+ for (i = 0; i < fmt_size; i++)
+ if (fmt[i] == '%') {
+ if (i + 1 >= fmt_size)
+ return -EINVAL;
+ if (fmt[i + 1] != 'd' && fmt[i + 1] != 'u' &&
+ fmt[i + 1] != 'x')
+ return -EINVAL;
+ fmt_cnt++;
+ }
+
+ if (fmt_cnt > 3)
+ return -EINVAL;
+
+ return __trace_printk((unsigned long) __builtin_return_address(3), fmt,
+ (u32) r3, (u32) r4, (u32) r5);
+}
+
+static struct bpf_func_proto tracing_filter_funcs[] = {
+ [BPF_FUNC_load_pointer] = {
+ .ret_type = RET_INTEGER,
+ },
+ [BPF_FUNC_memcmp] = {
+ .ret_type = RET_INTEGER,
+ .arg1_type = INVALID_PTR,
+ .arg2_type = PTR_TO_STACK_IMM,
+ .arg3_type = CONST_ARG_STACK_IMM_SIZE,
+ },
+ [BPF_FUNC_dump_stack] = {
+ .ret_type = RET_VOID,
+ },
+ [BPF_FUNC_trace_printk] = {
+ .ret_type = RET_INTEGER,
+ .arg1_type = PTR_TO_STACK_IMM,
+ .arg2_type = CONST_ARG_STACK_IMM_SIZE,
+ },
+ [BPF_FUNC_map_lookup_elem] = {
+ .ret_type = PTR_TO_MAP_CONDITIONAL,
+ .arg1_type = CONST_ARG_MAP_ID,
+ .arg2_type = PTR_TO_STACK_IMM_MAP_KEY,
+ },
+ [BPF_FUNC_map_update_elem] = {
+ .ret_type = RET_INTEGER,
+ .arg1_type = CONST_ARG_MAP_ID,
+ .arg2_type = PTR_TO_STACK_IMM_MAP_KEY,
+ .arg3_type = PTR_TO_STACK_IMM_MAP_VALUE,
+ },
+ [BPF_FUNC_map_delete_elem] = {
+ .ret_type = RET_INTEGER,
+ .arg1_type = CONST_ARG_MAP_ID,
+ .arg2_type = PTR_TO_STACK_IMM_MAP_KEY,
+ .arg3_type = PTR_TO_STACK_IMM_MAP_VALUE,
+ },
+};
+
+static const struct bpf_func_proto *tracing_filter_func_proto(enum bpf_func_id func_id)
+{
+ if (func_id < 0 || func_id >= ARRAY_SIZE(tracing_filter_funcs))
+ return NULL;
+ return &tracing_filter_funcs[func_id];
+}
+
+static const struct bpf_context_access {
+ int size;
+ enum bpf_access_type type;
+} tracing_filter_ctx_access[] = {
+ [offsetof(struct bpf_context, arg1)] = {
+ FIELD_SIZEOF(struct bpf_context, arg1),
+ BPF_READ
+ },
+ [offsetof(struct bpf_context, arg2)] = {
+ FIELD_SIZEOF(struct bpf_context, arg2),
+ BPF_READ
+ },
+ [offsetof(struct bpf_context, arg3)] = {
+ FIELD_SIZEOF(struct bpf_context, arg3),
+ BPF_READ
+ },
+ [offsetof(struct bpf_context, arg4)] = {
+ FIELD_SIZEOF(struct bpf_context, arg4),
+ BPF_READ
+ },
+ [offsetof(struct bpf_context, arg5)] = {
+ FIELD_SIZEOF(struct bpf_context, arg5),
+ BPF_READ
+ },
+};
+
+static bool tracing_filter_is_valid_access(int off, int size, enum bpf_access_type type)
+{
+ const struct bpf_context_access *access;
+
+ if (off < 0 || off >= ARRAY_SIZE(tracing_filter_ctx_access))
+ return false;
+
+ access = &tracing_filter_ctx_access[off];
+ if (access->size == size && (access->type & type))
+ return true;
+
+ return false;
+}
+
+static struct bpf_verifier_ops tracing_filter_ops = {
+ .get_func_proto = tracing_filter_func_proto,
+ .is_valid_access = tracing_filter_is_valid_access,
+};
+
+static struct bpf_prog_type_list tl = {
+ .ops = &tracing_filter_ops,
+ .type = BPF_PROG_TYPE_TRACING_FILTER,
+};
+
+static int __init register_tracing_filter_ops(void)
+{
+ /* init function offsets used to convert BPF_FUNC_* constants in
+ * BPF_CALL instructions to offset of helper functions
+ */
+ tracing_filter_funcs[BPF_FUNC_map_lookup_elem].func_off =
+ bpf_map_lookup_elem - __bpf_call_base;
+ tracing_filter_funcs[BPF_FUNC_map_update_elem].func_off =
+ bpf_map_update_elem - __bpf_call_base;
+ tracing_filter_funcs[BPF_FUNC_map_delete_elem].func_off =
+ bpf_map_delete_elem - __bpf_call_base;
+ tracing_filter_funcs[BPF_FUNC_trace_printk].func_off =
+ bpf_trace_printk - __bpf_call_base;
+ tracing_filter_funcs[BPF_FUNC_memcmp].func_off =
+ bpf_memcmp - __bpf_call_base;
+ tracing_filter_funcs[BPF_FUNC_dump_stack].func_off =
+ bpf_dump_stack - __bpf_call_base;
+ tracing_filter_funcs[BPF_FUNC_load_pointer].func_off =
+ bpf_load_pointer - __bpf_call_base;
+
+ bpf_register_prog_type(&tl);
+ return 0;
+}
+late_initcall(register_tracing_filter_ops);
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 9258f5a815db..bb7c6a19ead5 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -984,12 +984,15 @@ struct ftrace_event_field {
int is_signed;
};
+struct sk_filter;
+
struct event_filter {
int n_preds; /* Number assigned */
int a_preds; /* allocated */
struct filter_pred *preds;
struct filter_pred *root;
char *filter_string;
+ struct sk_filter *prog;
};
struct event_subsystem {
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index f99e0b3bca8c..54298a0ad272 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1075,6 +1075,13 @@ event_filter_write(struct file *filp, const char __user *ubuf, size_t cnt,
err = apply_event_filter(file, buf);
mutex_unlock(&event_mutex);
+ if (file->event_call->flags & TRACE_EVENT_FL_BPF)
+ /*
+ * allocate per-cpu printk buffers, since eBPF program
+ * might be calling bpf_trace_printk
+ */
+ trace_printk_init_buffers();
+
free_page((unsigned long) buf);
if (err < 0)
return err;
diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 8a8631926a07..66e7b558ccae 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -23,6 +23,9 @@
#include <linux/mutex.h>
#include <linux/perf_event.h>
#include <linux/slab.h>
+#include <linux/bpf.h>
+#include <trace/bpf_trace.h>
+#include <linux/filter.h>
#include "trace.h"
#include "trace_output.h"
@@ -535,6 +538,16 @@ static int filter_match_preds_cb(enum move_type move, struct filter_pred *pred,
return WALK_PRED_DEFAULT;
}
+void trace_filter_call_bpf(struct event_filter *filter, struct bpf_context *ctx)
+{
+ BUG_ON(!filter || !filter->prog);
+
+ rcu_read_lock();
+ SK_RUN_FILTER(filter->prog, (void *) ctx);
+ rcu_read_unlock();
+}
+EXPORT_SYMBOL_GPL(trace_filter_call_bpf);
+
/* return 1 if event matches, 0 otherwise (discard) */
int filter_match_preds(struct event_filter *filter, void *rec)
{
@@ -794,6 +807,8 @@ static void __free_filter(struct event_filter *filter)
if (!filter)
return;
+ if (filter->prog)
+ sk_unattached_filter_destroy(filter->prog);
__free_preds(filter);
kfree(filter->filter_string);
kfree(filter);
@@ -1898,6 +1913,48 @@ static int create_filter_start(char *filter_str, bool set_str,
return err;
}
+static int create_filter_bpf(char *filter_str, struct event_filter **filterp)
+{
+ struct event_filter *filter;
+ struct sk_filter *prog;
+ long prog_id;
+ int err = 0;
+
+ *filterp = NULL;
+
+ filter = __alloc_filter();
+ if (!filter)
+ return -ENOMEM;
+
+ err = replace_filter_string(filter, filter_str);
+ if (err)
+ goto free_filter;
+
+ err = kstrtol(filter_str + 4, 0, &prog_id);
+ if (err)
+ goto free_filter;
+
+ err = -ESRCH;
+ prog = bpf_prog_get(prog_id);
+ if (!prog)
+ goto free_filter;
+
+ filter->prog = prog;
+
+ err = -EINVAL;
+ if (prog->info->prog_type != BPF_PROG_TYPE_TRACING_FILTER)
+ /* prog_id is valid, but it's not a tracing filter program */
+ goto free_filter;
+
+ *filterp = filter;
+
+ return 0;
+
+free_filter:
+ __free_filter(filter);
+ return err;
+}
+
static void create_filter_finish(struct filter_parse_state *ps)
{
if (ps) {
@@ -2007,7 +2064,20 @@ int apply_event_filter(struct ftrace_event_file *file, char *filter_string)
return 0;
}
- err = create_filter(call, filter_string, true, &filter);
+ /*
+ * 'bpf_123' string is a request to attach eBPF program with id == 123
+ * also accept 'bpf 123', 'bpf.123', 'bpf-123' variants
+ */
+ if (memcmp(filter_string, "bpf", 3) == 0 && filter_string[3] != 0 &&
+ filter_string[4] != 0) {
+ err = create_filter_bpf(filter_string, &filter);
+ if (!err)
+ call->flags |= TRACE_EVENT_FL_BPF;
+ } else {
+ err = create_filter(call, filter_string, true, &filter);
+ if (!err)
+ call->flags &= ~TRACE_EVENT_FL_BPF;
+ }
/*
* Always swap the call filter with the new filter
--
1.7.9.5
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